Patent GB-600686-A (GB)
Title: Carburetors
IPC: F02M69/00
Filed: 1945-10-02
Abstract: 600,686. Spray carburetters. BENDIX AVIATION CORPORATION. Oct. 2, 1945, No. 25518. Convention date, May 31, 1944. [Class 7 (iii)] In a carburetter in which the flow of fuel under pressure is controlled by a fuel valve operated by pressure responsive elements, one of which is subjected to an air pressure which varies with the air flow in the induction passage tending to open the valve and another of which is subjected to a fuel pressure which varies with the fuel flow tending to close the valve, the valve is controlled by both elements when the air flow is above a certain value, but below this air flow the valve is controlled only by the fuel pressure, a substantially constant force being substituted for the air metering force produced by the element responsive to air pressure. The two elements may act as a unit to control the fuel valve above a certain air flow while below this flow independent movement of the fuel valve and the element subjected to fuel pressure is permitted with respect to the other element. As shown, fuel under pressure is supplied to an inlet connection 38 from which it passes through a fuel valve 42 into a chamber D and then into a pipe 90, fuel control body 13, part 103 and pipe 103a to a discharge nozzle 26 opening in the induction passage. The fuel valve 42 is controlled by diaphragms 30, 34 of a regulator 12. Diaphragm 30 is operated on by entering air pressure in a chamber A and suction from a venturi 18 in chamber B. A diaphragm 45 is provided between the valve 42 and fixed member 44, 46. Should this diaphragm rupture, the fuel flow to the carburetter from a chamber 51 is restricted by orifices 51a. Chambers A and B are interconnected by a bleed passage 20c containing small orifices. The interconnection in conjunction with a valve 14a controlled by a capsule enables the fuel flow to be modified with variation of altitude to give the desired mixture strength. The fuel control body includes a valve 91 interconnected with the throttle valves by means of an arm 93. From this valve the fuel flows to jets 96, 97, 98, 99 and a valve 101. From the jets fuel passes to a manually-controlled valve 104 for varying the fuel flow and thus controlling the strength of the mixture supplied by the carburetter. Jet 99 is controlled by a valve 100 forming part of a water metering system, not shown. The valve 101 opens when the difference between metered and unmetered fuel pressure attains a predetermined value. Jet 97 controls the fuel flow at high flows. Metered fuel pressure is transmitted to the chamber C by a pipe 107. The throttle valves 23 are partly masked by the induction passage at 25 when near the closed position so that the speed of opening is for a given speed of throttle operation lower at small openings than during the remainder of the range of movement. An accelerator pump 28 operated by the throttle or other means is provided and when this pump is operated, pressure is applied to the diaphragm 66, by means of a channel 76 which places the left-hand side of the diaphragm in communication with a piston chamber in the accelerator pump. Diaphragm 34 is operated on respectively by metered and unmetered fuel pressures in chambers C and D. Diaphragm 34 is positively connected to an operating rod 55 of the valve through a bearing 54. Diaphragm 30 is not positively connected to the diaphragm 34, but the two diaphragms act as a single unit above a certain air flow when a shoulder 52a on a member 52 secured to the diaphragm 34 engages a bearing 60 secured to a member 57 attached to the diaphragm 30. The diaphragms are held in this abutted position by the fuel and air pressures. A spring 59 within a member 58 attached to the member 57 associated with the diaphragm 30 tends to urge the diaphragms apart and thus to part the shoulder 52a and the bearing 60. A stop member 67 is rigidly connected to the diaphragm 30 and when the airflow drops to a predetermined value below cruising range, the diaphragm 30 has moved to the left sufficiently for the member 67 to contact a stop 72. After this, the fuel diaphragm 34 can move with respect to the air diaphragm by compressing the spring 59 and the spring provides a force tending to keep the valve 42 open and provide the correct fuel flow for idling conditions. A member 75 sliding within an extension of the member holding the spring 59 serves as a guide. A diaphragm 63 is connected between a partition 32a between chambers B and C and the member 57 associated with the diaphragm 30 and the diaphragm 66 is connected between a hub member 31a and a member 65 connected to the diaphragm 30. The pressures on these two diaphragms balance one another. The stop 72 is adjustable and can be locked by a locking plate 73 having a cover member 74. A chamber 37 is provided in front of the valve 42 and this contains float-operated vapour separating valves 81. Vapour passes back to the fuel tank by a passage 83. A fuel strainer 39 is included. When the valve 104 is turned to an idle cut-off position, a channel 106 is closed and pressure builds up in chamber D sufficiently to close the valve 42. Specification 523,895 is referred to.